RU2694770C1 - Method for processing bottom sediments in a reservoir - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil industry, in particular, to a method for treating bottom sediments in a reservoir. Method involves feeding the solvent into a reservoir, stirring the precipitate with the solvent, settling the precipitate mixture with the solvent and pumping out the liquid hydrocarbon phase. Volume of bottom sediments is determined prior to solvent pumping. Solvent is fed simultaneously with mixing bottom sediments. Solvent used is an oil paraffin solvent, which is a gasoline fraction with a boiling point of not less than 28 °C and temperature of 90 % distillation not higher than 240 °C, or an industrial solvent, which is a by-product of the catalytic reforming process, which is a mixture of aromatic, naphthenic and paraffin hydrocarbons, with content of aromatic hydrocarbons of not less than 8 % (weight). Solvent is fed in amount of 25–30 % of the bottom sediment volume. Mixing of mixture of bottom sediments and solvent in reservoir is performed during 7–10 days. Settling of mixture in reservoir is carried out for 7–10 days. Obtained liquid hydrocarbon phase is pumped to oil treatment plant.

EFFECT: extraction of additional volume of oil from bottom sediments due to increased efficiency of bottom sediments treatment in reservoir, reduction of losses of valuable hydrocarbon raw material, production of liquid hydrocarbon phase with low content of mechanical admixtures and water.

1 cl, 1 dwg, 1 tbl

Description

The proposal relates to the oil industry, in particular to methods for extracting oil from bottom sediments accumulated in tanks of oil treatment plants and product parks.

A known method of cleaning tanks from bottom sediments (patent RU No. 2442632, IPC B01D 17/00, publ. 02/20/2012), including the supply of oil to the bottom of the tank, removal of the resulting mixture from the bottom of the tank, followed by heating it in a heat exchanger and multiple circulation according to the “tank-heat exchanger-flow distributor” scheme. Additionally, the mixture can be subjected to ultrasonic treatment and enter into it a paraffin dispersant or a depressant additive.

The disadvantages of this method are the low efficiency of extraction of hydrocarbons contained in the bottom sediments, the need for additional heating and ultrasonic treatment, a high content of solids and water in the liquid hydrocarbon phase.

There is a method of treating bottom sediments in the tank, which includes supplying the solvent to the tank, mixing the precipitates with the solvent, settling the precipitate mixture with the solvent for 8-10 hours and pumping out the liquid hydrocarbon phase. In this case, the remaining residue is heated by direct contact with the coolant. As a coolant, an oil solvent is used, for example, oil, kerosene, diesel fuel (application RU No. 96107765, IPC В08В 9/08, publ. 27.06.1998).

The disadvantages of this technology are:

- low processing efficiency of bottom sediments in the tank, as there remains a high content of mechanical impurities and water in the liquid hydrocarbon phase;

- the need to install additional equipment for heating the solvent;

- increase energy consumption;

- high economic costs of technology implementation.

A known method of treating bottom sediments includes the supply of a solvent, mixing the precipitates with a solvent, settling the precipitate mixture with a solvent and pumping the liquid hydrocarbon phase (RU Patent No. 2654545, IPC C10G 1/04, publ. 04/20/2001 in bulletin No. 11). As a solvent, a mixture of distillation fractions of oil with a boiling point of 50-220 ° C is used, which is introduced into the slurry to achieve a constant density of the slurry solution. The slurry solution is treated with an aqueous solution of flocculant in a ratio of 10: 1, followed by settling.

The disadvantages of this method are:

- the complexity of the method of processing bottom sediments, requiring the construction of additional tanks, pipelines, change the input for the solvent;

- the need for continuous monitoring of the density of the mixture of solvent and bottom sediment;

- high solvent consumption;

- high economic costs for the implementation of the method.

The closest analogue is the method of treating bottom sediments, including the supply of a solvent and the sedimentation of a mixture of precipitates with a solvent (US Patent No. 4017377, IPC C10G 1/04, publ. 12.04.1977).

The disadvantage of this method is not a high degree of extraction of oil from bottom sediments in the tank.

The technical objectives of the present invention are: extracting additional oil from bottom sediments by increasing the processing efficiency of bottom sediments in the tank, reducing the loss of valuable hydrocarbons, obtaining a liquid hydrocarbon phase with low content of mechanical impurities and water, improving the performance of the tank, expanding the technological capabilities of the method due to use as a solvent product of its own production, reducing the cost of cleaning the reservoir sediments and utilization of bottom sediments.

The tasks are solved by the method of treating bottom sediments in the tank, which includes supplying the solvent to the tank, mixing the sediments with the solvent, settling the precipitate mixture with the solvent and pumping out the liquid hydrocarbon phase.

New is the fact that before the injection of solvent, the amount of bottom sediments is determined, the solvent is fed simultaneously with the mixing of bottom sediments, the solvent used is paraffin oil solvent, which is a gasoline fraction with an initial boiling point not lower than 28 ° C and a temperature of 90% distillate not higher 240 ° C, or industrial solvent, which is a byproduct of the catalytic reforming process, which is a mixture of aromatic, naphthenic and paraffinic hydrocarbons, with с Keeping aromatic hydrocarbons at least 8% (by weight), the solvent is fed in the amount of 25-30% of the volume of bottom sediments, mixing of the mixture of bottom sediments and solvent in the tank is carried out for 7-10 days, settling of the mixture in the tank is carried out for 7- 10 days, the resulting liquid hydrocarbon phase is pumped to the oil treatment installation.

The figure shows a tank diagram with an indication of the process flow for the treatment of bottom sediments.

The scheme contains a tank 1, a solvent supply nozzle 2, a mixing device 3, a pumping pump 4, a gauge hatch 5, a pre-dewatering unit 6.

The essence of the method is as follows.

The oil is pumped out of the tank 1 through the pump 4 to the minimum level at which the mixing device 3 can work. As a mixing device, a device is used to scour the Typhoon type bottom sediments. According to the calibration table of the tank determine the amount of bottom sediments. Include mixing device 3 and at the same time through the fitting of the solvent supply serves the solvent I in the amount of 25-30% of the volume of bottom sediments. The solvent used is a product of its own production: petroleum paraffin solvent (RPN), which is a gasoline fraction with a high content of normal and isomeric paraffin hydrocarbons, which determines the high solubility of the RPN with respect to paraffins and its ability to extract the hydrocarbon phase from bottom sediments, with temperature the beginning of the boil is not below 28 ° C; temperature of 90% distillation is not higher than 240 ° C, washing ability of 76.8% at 20 ° C (T - 120 min) (table 1), which is produced at the complex oil treatment unit according to TU 0251-062-00151638-2006, or solvent industrial (RP), which is a by-product of the catalytic reforming process, which is a mixture of aromatic, naphthenic and paraffin hydrocarbons, with an aromatic hydrocarbon content of at least 8% (by weight), washing ability of 85.6% at 20 ° С (T - 120 min ), obtained at the refinery installation according to TU 0258-007-06320171-2016.

In practice, solvents containing heavier hydrocarbons are commonly used, as a result of which their effectiveness as a solvent for paraffins is lower. Then continue stirring the mixture of bottom sediments and solvent for 7-10 days, after which they defend the mixture for 7-10 days. The duration of mixing and settling is determined by the effectiveness of the separation of the mixture into a liquid hydrocarbon part and the residue, which is determined by the level of bottom sediments through the gauge hatch 5, for example, manually using a tape measure with a lot or any other known method. Upon completion of mixing and settling of the mixture of bottom sediments and solvent, the volume of the liquid hydrocarbon phase is at least two volumes of the injected solvent. Then assess the quality of the hydrocarbon phase by layer-by-layer sampling every 0.3-0.5 m.

The quality of the hydrocarbon phase is estimated by the indicators of the mass fraction of water and mechanical impurities. If the mass fraction of water in the liquid hydrocarbon phase is less than 5%, the content of mechanical impurities is less than 0.2%, then the hydrocarbon phase II is pumped out using a pump 4 to exit the pre-dewatering unit 6 for mixing with the previously dehydrated oil. In this case, the volume fraction of the liquid hydrocarbon phase in the mixture with the previously dehydrated oil should not exceed 10%.

If the mass fraction of water in the liquid hydrocarbon phase is more than 5%, the content of mechanical impurities is less than 0.2%, then the hydrocarbon phase II is pumped to the inlet of the preliminary dewatering unit 6 for mixing with the production of wells and subsequent preliminary dewatering. In this case, the volume fraction of the liquid hydrocarbon phase in the mixture with the production of wells should not exceed 10% of the volume of the incoming emulsion (excluding "free water").

An example of a specific implementation of the proposed method.

At the product park, oil was pumped out of the tank through the pump to the minimum level at which the mixing device can work. As a mixing device, a device was used to wash out bottom sediments such as "Typhoon". Determined the volume and composition of bottom sediments. The volume was 1023 m ³ . The composition of bottom sediments is as follows: mass fraction of water - 6.9%, mechanical impurities - 1.7%, asphaltenes - 1.8%, paraffins - 23.9%, resins - 9.7%, oils - 56%. Then they switched on the mixing device and started feeding into the tank through the RPN or RP nipple in the amount of 280 m ³ . The solvent was pumped into the propeller area of the mixing device with constant mixing of bottom sediments and solvent. After the solvent was fully injected, stirring was continued for 7 days. After stopping the mixing device, the mixture of bottom sediments with solvent was settled for 7 days. Then, sampling of the liquid hydrocarbon phase was performed at reservoir levels with an interval of 0.5 m. It was established that in samples from levels in the range of 2.5–4 m, the mass fraction of water was 0.26–0.6%, the mass fraction of mechanical impurities was 0 , 04%. In the sample from the level of 2 m, the mass fraction of water was 15.5%, the mass fraction of mechanical impurities - 0.18%. In the sample from the level of 1.9 m, the mass fraction of water was 19.1%, the mass fraction of mechanical impurities - 0.41%. The liquid hydrocarbon phase was pumped to the level of 2 m. The share of the hydrocarbon phase extracted from the bottom sediments was 503 m ³ (without taking into account the solvent volume). The volume of bottom sediments decreased to 520 m ³ , i.e. 1.97 times. The residue is a concentrate of mechanical impurities, water and high-molecular components. He was sent to the installation processing the bottom sediments. The implementation of the technology allowed to extract an additional 397 tons of oil. The economic effect of the event was 4,293.3 thousand rubles.

The proposed method of processing bottom sediments in the tank has the following advantages:

- firstly, it allows extracting additional volume of oil from bottom sediments and reducing losses of valuable hydrocarbon raw materials;

- secondly, it allows to obtain a liquid hydrocarbon phase with a low content of mechanical impurities and water;

- thirdly, increases the performance of the tank;

- fourthly, it expands the technological capabilities of the method by using the product of its own production as a solvent;

- fifthly, it reduces energy consumption and the cost of cleaning the tank and disposing of bottom sediments.

Claims (1)

The method of treating bottom sediments in the tank, which includes supplying the solvent to the tank, mixing the precipitates with the solvent, settling the precipitate mixture with the solvent and pumping out the liquid hydrocarbon phase, characterized in that before the solvent is injected, the volume of the bottom sediments is determined, and the solvent is mixed simultaneously with the mixing of the bottom sediments the solvent used is a paraffin oil solvent, which is a gasoline fraction with an initial boiling point not lower than 28 ° C and a temperature 90% of the distillate is not higher than 240 ° C, or industrial solvent, which is a by-product of the catalytic reforming process, which is a mixture of aromatic, naphthenic and paraffinic hydrocarbons, with an aromatic hydrocarbon content of at least 8% (by weight), the solvent is fed in an amount of 25-30 % of the volume of bottom sediments, mixing of the mixture of bottom sediments and solvent in the tank is carried out for 7-10 days, settling of the mixture in the tank is carried out for 7-10 days, the resulting liquid hydrocarbon phase is pumped out t on the installation of oil treatment.

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